Control means for the blades of the sustaining rotor of a rotary-wing aircraft



Jan. 10,1950 R. HAFNER -CONTROL MEANS, FOR THE BLADES OF THE SUSTAININGROTOR OF A ROTARY-WING AIRCRAFT 2 Sheets-Sheet 1 Filed June 3, 1947 Jan.10, 1950 R. HAFNER 2,493,869

CONTROL MEANS FOR THE BLADES OF THE SUSTAINING ROTOR OF A ROTARY-WINGAIRCRAFT 2 Sheets-Sheet 2 Filed June 5, 1947 gar??? Patented Jan. 10,,1950

enssisss nGONFLROL MEANS FOR THE IITADESFOFL'IHLE SUSTAIN IN G ROFIZOR0F*A :ROTARX WING AIRQRAET *Raoul Ha'fner, Bristol, England, ass'ignorto The 'Br'ist6l Aer-oplane Company Eimitd, Bristol, fiEng-laxfdga:British company ApplicationIJuna3, 1947,ISeriahNmJZ52j263 In GreatBritain Mayl30, 194'6 SectionrlxBdblic Law 690, August 8, 1946 w Patentexpires May 30,:I9'66 l "5"Claims. invention concerns .rotary-w-ing.aircraft and more.- .par.ticu1arly.helicopters.

In rotary-wing aircraft -.it is .lcommon. practice to mountvear'ihblafde.ona ro-torhu-bso thatitl. is capable of independent=vertica1 smovements '(hereinaiterreferred' toras 'fiappingi movements)The .flapping movements of the. blades vary .with variations in x thelift and centrifugal Qforce, amongst dither .faotors, and .stops .areusually provided to limit .the amplitude .o'f such movemerits. 5 Duringnormal 'Jflight conditions the blades usuallyperformLtheirLfiapDingmovements between an upper and alowerlfixed stop. When the aircra'tt isat rest .(withLLthe rotor stationary or rotating atlow speeds) theblades engagethe lower stops andhare supported' by them vso that theyare-kept olearo'i the "fuselage or other part of'the' machine.

Inifiig'ht, a"blade of therotor maybe struck by agust so that. adownward flapping movement To provide :for this contingency the'lowerstop has lieretoforebeen" vertically spaced 'from the rotor by "aconsiderable amount .so that under such adverse'con'ditionsthebladesdoesnot strikeithe stop.

"Theconstructiontof'the'rotorblades is such that when they are'stati'onary"'their flexibility :resiilts in each blade being"downwardly curved towards the aircraft. 'This "requires that *thevertical distance *between the lower "stops "and the rotor be small"arid/or that the stops "be dispose'dat 'a-'-cons'iderab1e radialdistance "from the rotor -a'xis in-==order to minimise the droop.

Up "to -now it "has 'th'erefore been "considered necessary' in' ofiderto a1lowiforadverse' fii'ght'conditions that the lower s'tops bevertieal'ly spaced from th'e rotor by a considerable amount and that,"in order to eount'eract the ifdroop :of th-e blades *whilst zat:reshdzhis "vertical "distanoe be madesmall'contlxatitheradialrdistance' to the-stops be-rz grea't.

:11; is an object :of invention :to provide lower stops for thesflapping blades which will effectively vsuppert the blades whilst theyare at: restandiimwhiehthe vertical distance between the steps land'lthe lrotor ,is'ssmall. .In thiswway it 'risiensured that :the heightsof -.theI-2rotor ia-beve the fuselage :is .rreduced whereby the-..dra-g -:.of the-laircrattsbecomes less-withoutincreasing the (Cl.I'm-160152) 2 risk of the blades "striking the ifus'elage when they-droop.

sAccordingsto one aspect :ofthepresent invention a rotor assembly for arotary-wingaircraftmomprises two or :more blades which erform a flappingmovementrand a:stoptmember common to. at .leastiaspai'r obit-lappingblades tolimittheir downward movement, -:said :memb er beingwhara'cterised :in -:that aon -zits sengagement ;by -ether than all e ofthe blades tto wwhic-h it is comm'on it .-i-s [displaced sto allow thesevblades ltoemove downwardly and upon its engagementeby allsof the bladesto'whicheit is common itsis not-so displaced and l-imits the 'down-ward:-movement of :all said blades.

rnccording to-anotherz aspeet Of thEpIDI'BSBHtv'IH- vention amo'torassembly: for: a ZIlGt'fiIEY-Whifgflifcraft *wherein "therrotor :bladeseach 'lperf'orm ra' fiappingrmovement; the-idownward limit of -which isdetermined by asstop-zmemberpisi:dharacterised in that :th'e'rstop'Jmem'ber ismoimnon it!) all "the blades and is resiliently mountediandd-isplaca ablei-on engagementrbydess than all the blades.

i'Preferably theestop me'mber icemprises'ianrrin'g whioh'iis resiliently mounted i orr rotation witlritiie roltor h-db. The tin-g 'anay emounted on a rubber ring or "a plural-ity 6f *ru'bb'er blooks orbrishes' spaced aroun d it or alternatively'springs may be provided.

The'stop iing'and' carriertherei'or may beprovi-de'd with-surfaces whiehare inclined with respeot to the 'axis'df rotation of the rotor, theresilient "material lying between said inclined faces. *Preferably "theouter "peripheral surface of thestop iingis' engage-able" by 'armsprojecting from each blade. Said peripheral surface is preferably"disposed'iatcas "great awatdieildistance from the rotor as "ispracticable "and Small for'examplegbeflisposed.so as to lie.betwe'entheflapping and drag axes 'ofthe :blades.

rotor assembly in accordance wlthlthisimzeiition showing.lcertamdetailsiinl diagrammaitimmanner,

.-'.Eigure -2-.is Marni-aw inlithe idireotionsofnarrowi of Figure J,sand partak-es of several different movements.

' stop 2| carried by the hub I I.

Figure 3 is a section on the line 3-3 of Figure 2, certain parts beingshown in elevation for the sake of clarity.

Referring to Figure 1: a pylon member 5 is attached to the upper surfaceof the fuselage 6 and supports, by suitable bearings (not shown) asleeve -1. The sleeve carries a gear 8 and power is transmitted from anengine mounted within the fuselage 6 to a shaft 9 and thence by a pinionID to the gear 8 and so to the rotor hub II, the latter being bolted tothe driving sleeve 7. The rotor hub, inknown manner, is provided with aplurality of blades l2''-in the present case three-each of whichindependently Thus the blades as a whole rotate in the direction ofarrow at about the axis a. Each blade performs a flapping movement I)about axis b and a drag movement about axis 0' whilst the-pitch of theblade may be varied by adjusting it in the direction of arrow d aboutaxis d.

To permit of each blade performing the flapping movement I) it isattached at its root end to a lug l3 which is pivotally secured to thehub H by a pin [4. In practice the blade I2 is attached to the lug [3through the agency of an element l which is pivotally mounted to the lugl3 so that the blade may perform the drag movements about axis 0.

' Referring now to Figure 3, it will be observed that the upperextremity of the driving sleeve I has bolted to it a ring H5. The latterlies immediately below the lugs 13. The downwardly directed surface ofthe ring is is inclined with respect to the long axis of the pylon 5 i.c. with respect to the axis a. A second ring I! is disposed beneath thefirst ring and is similarly formed with an inclined face, which,however, is upwardly directed. The two inclined faces are thereforedirected towards each other and there is carried between them a rubberring I8. .The

ring 18 is bonded to the carrier l6 and has bonded to it'the ring I1 sothat the latter is supported from the carrier solely by the rubber ring.The ring I! constitutes one element of a stop which is provided to limitthe downward flapping movements of the blades I2.

. eral edge of the ring I! is at a greater radial distance from the axisof rotation of the rotor than the flapping axis b and is at a lesserdistance from the rotor axis than the drag axis 0'. With thisarrangement when a blade l2 drops to a predetermined position the fingerl9 will engage the peripheral edge of the stop ring I! and its furtherdownward movement will be limited as hereinafter described.

The lugs l3 are each formed with a finger 20 on their upper surfacewhich is engaged by a The function of the fingers 20 and stops 2| is tolimit the upward movement of the blades during flapping.

From what has been said it will be appreciated that when a blade I2moves downwardly so that its finger l9 engages the stop ring I! thelatter will be displaced sideways i. e. tilted relatively to theinterposition of a certain setting of the flight controls, the fingers 4I!) will be raised clear of the stop ring [1. As the rotor comes to restthe blades will all engage the stop ring and will as a result, be heldup by it. However, during flight or at other times should one blade onlyengage the stop ring, the ring is tilted and has no effect in preventingthe down ward flapping movement of such a blade. Thus, the verticalheight from the rotor to the stop ring may be small since if a singleblade strikes the stop ring because of adverse flight conditions thering is displaced. However, the stop is effective to support the bladeswhen all of them engage it so' as to maintain the blades clear of thefuselage when they droop.

With the arrangement described the height of the pylon 5 may be reducedand as a consequence the drag of the aircraft may be made less.

It will be clear that instead of the rubber ring l8 springs or rubberbushes or blocks may be provided.

I claim:

1. A rotor assembly for a rotary-wing aeroplane comprising a rotor hub,means to drive the hub, at least two blades carried by the hub forrotation therewith, a hinge member for each blade by which it isattached to the hub for flapping movement, a structure engageable by theblades to limit their downward flapping movement and resilient means bywhich said structure is supported for rotation with the hub whereby, onflapping of the blades, engagement of the structure by less than all ofthe blades displaces the structure towards the other blade.

2. A rotor assembly for a rotary-wing aeroplane comprising a rotor hub,means to drive the hub, at least two blades carried by the hub forrotation therewith. a hinge member for each blade by which it isattached to the hub for flapping movement, a structure engageable by theblades to limit their downward flapping movement and resilient means bywhich said structure is supported for rotation with the hub whereby, onflapping of the blades, engagement of the structure by less than all ofthe blades displaces the structure towards the other blades.

3. A rotor assembly for a rotary-wing aeroplane comprising a rotor hub,means to drive the hub, at least two blades carried by the hub forrotation therewith, a hinge member for each blade by which it isattached to the hub for flap ping movement, a ring beneath the hub andnormally disposed co-axially of the axis of rotation of the rotor,resilient means securing the ring to the hub for rotation therewith andpermitting limited transverse movements of the ring and adownwardly-directed projection from each blade to engage the edge ofsaid ring, each blade being capable of a downward flapping movement inexcess of that at which the blade'projection engages the ring thereby todisplace the ring towards the other blade projections.

' 4. A rotor assembly for a rotary-wing 'aero-iplane according to claim3 wherein the ring has an inwardly directed conical face and adiscmember is carried by the hub said disc having a correspondinglyformed conical face, the ring being supported from the disc by a rubberbush secured to said conical faces.

5. A rotor assembly for a rotary-wing aeroplane as claimed in claim 4wherein the edge of the ring is at agreater radial distance from theaxis of rotation of the rotor than the axis about which the flappingmovements take place and is at a smaller radial distance than the axisabout which the drag movements of the blade take Number Name Date place.2,151,215 Larsen Mar. 21, 1939 RAOUL HAFNER. 2,265,366 Hafner Dec. 9,1941 2,396,038 Bossi Mar. 5,1946 REFERENCES CITED 5 2,430,767 HirschNov. 11, 1947 The following references are of record in the FOREIGNPATENTS file of this patent: Number Country Date UNITED STATES PATENTS438,111 Great Britain Nov. 12, 1935 Number m Date 10 487,811 GreatBritain June 27, 1938 1,985,819 Cierva Dec. 25, 1934

